How should you use fields in a child class JS?

When I declare fields in the child class, and then access them with this it breaks.
I have tried the big arrow

This is a simplified example example

class Shape
{
  
}

class Polygon: Shape {
  name;
  constructor() {
    this.name = 'Polygon';
  }

  cout()
  {
    console.log(this.name);
  }
  
}

const poly1 = new Polygon();

poly1.cout(); // returns an error
// Expected output: "Polygon"